Common Core: 7th Grade Math : Geometry

Study concepts, example questions & explanations for Common Core: 7th Grade Math

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Example Questions

Example Question #4 : Know And Use The Formulas For The Area And Circumference Of A Circle: Ccss.Math.Content.7.G.B.4

The diameter of a circle is . Give the area of the circle in terms of .

Possible Answers:

Correct answer:

Explanation:

The area of a circle can be calculated using the formula:

,

where   is the diameter of the circle and is approximately .

Example Question #1 : Area Of A Circle

The radius of a circle is  . Give the area of the circle.

Possible Answers:

Correct answer:

Explanation:

The area of a circle can be calculated as , where   is the radius of the circle, and is approximately .

Example Question #1 : Area Of A Circle

The circumference of a circle is inches. Find the area of the circle.

Let .

Possible Answers:

Correct answer:

Explanation:

First we need to find the radius of the circle. The circumference of a circle is , where is the radius of the circle. 

 

The area of a circle is where   is the radius of the circle.

Example Question #1 : Radius

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The radius of a circle is 4 cm, what is the area?

Possible Answers:

Correct answer:

Explanation:

The area of a circle is found by: , where r is the radius.

.

The area of the circle is .

Example Question #1 : Radius

The radius, , of the circle below is 18 units. What is the area of the circle?

Circle

Possible Answers:

 square units

 square units

Cannot be determined

 square units

 square units

Correct answer:

 square units

Explanation:

The formula for the area, , of a circle with radius  is:

We can fill in 

You could do the arithmetic to get an area of about 1,017.876 square units, but it is ok and more precise to leave it as shown.

Example Question #1 : How To Find The Area Of A Circle

Give the area of a circle with diameter 13.

Possible Answers:

Correct answer:

Explanation:

Half of the diameter 13 is the radius . Use the area formula:

Example Question #402 : Geometry

How many times greater is the area of a circle with a radius of 4in., compared to a circle with a radius of 2in.?

Possible Answers:

4

2\pi

2

4\pi

Correct answer:

4

Explanation:

The area of a circle can be solved using the equation A=\pi r^{2} 

The area of a circle with radius 4 is \pi 4^{2}=16\pi while the area of a circle with radius 2 is \pi 2^{2}=4\pi. 16\pi \div 4\pi =4

Example Question #11 : Area Of A Circle

Find the area of a circle that has a radius of .

Possible Answers:

Correct answer:

Explanation:

Use the following formula to find the area of a circle:

For the circle in question, plug in the given radius to find the area.

In our particular case the radius is .

When squarring a fraction we need to square both the numerator and the denominator.

Example Question #12 : Area Of A Circle

Find the area of a circle that has a radius of .

Possible Answers:

Correct answer:

Explanation:

Use the following formula to find the area of a circle:

For the circle in question, plug in the given radius to find the area.

In this problem the known radius is 

Now plug the radius into the area equation.

Therefore we get,

Recall that when a square root is squared you are left with the number under the square root sign. This happens because when you square a number you are multiplying it by itself. In our case this is,

.

From here we can use the property of multiplication and radicals to rewrite our expression as follows,

and when there are two numbers that are the same under a square root sign you bring out one and the other number and square root sign go away.

 

Example Question #11 : How To Find The Area Of A Circle

What is the area of a circle with a diameter of , rounded to the nearest whole number?

Possible Answers:

\dpi{100} 81

\dpi{100} 64

\dpi{100} 255

\dpi{100} 254

Correct answer:

\dpi{100} 64

Explanation:

The formula for the area of a circle is

\dpi{100} \pi r^{2}

Find the radius by dividing 9 by 2:

\dpi{100} \frac{9}{2}=4.5

So the formula for area would now be:

\dpi{100} \pi r^{2}=\pi (4.5)^{2}=20.25\pi \approx 63.6= 64

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